1. Field of the Invention
The present invention relates to a method and apparatus for enhancing the resolution of digital image capture devices such as CCD scanners and digital cameras. More particularly, the present invention relates to a method and apparatus which multiplexes picture elements.
2. Description of Related Art
There has been a continuing need in the art of image capture to increase the resolution of a captured image without significantly increasing the cost and complexity of the image capture apparatus. An example of an application where increased resolution is often desirable is in teleconferencing. A low resolution image of the face of a conference participant is usually adequate for effective communication. However, where a document or an article exhibit is to be shared in a tele-conference, much higher resolution of the text or article details are usually desired. Accordingly there is a need for an effective means and method of increasing resolution without significantly increasing cost and complexity at either end of the conference.
U.S. Pat. No. 4,103,109 relates to the multiplexing of image picture elements from a parallel CCD capture array onto a single output line in a more efficient way. This reference does not improve the resolution of the image captured by the CCD array.
U.S. Pat. No. 5,541,653 issued to Peters et al. relates to increasing resolution of digital color images using a beam splitter on the image side of the lens to create multiple offset images which are later combined electronically to create an image of xe2x80x9cenhanced resolutionxe2x80x9d. A major disadvantage of the system of Peters is the need for high precision in the beam splitter and its placement. As a result of the requirement for high precision, commercial application of the technique of Peters is costly.
U.S. Pat. No. 5,502,578 issued to Smitt relates to an optical scanner having a variable apparent resolution. The varying resolution is obtained by varying the pixel and line sampling clock rates at differing amounts. The distances between CCD elements is fixed however and therefore actual sampling resolution must be fixed in this teaching.
U.S. Pat. No. 4,920,418 issued to Robinson relates to a scanning imaging system that includes an image shifting means between the lens and a CCD array. The image shifter which may be a rotatable glass plate driven by a piezoelectric bimorph, shifts an image of the object by less than the distance between adjacent PELS at the image plane. As a result of placement of the shifting device on the image side of the lens, expensive parts of close tolerances are required. Accordingly these systems have not achieved wide commercial success.
U.S. Pat. No. 5,449,898 issued to Dosmann relates to a test strip color and/or reflectance analyzer used in the field of clinical chemistry. The equipment of Dosmann is not increasing the resolution of an meaningful image but is detecting the existence of certain colors or reflectance with increased resolution. Accordingly, Dosmann is not concerned with the problem of how to combine or stitch together the partial fields 50a and 50b into a meaningful image. If Dosmann looks at a one half inch overlap field more than once to detect the presence of a color, it does not adversely affect the resultant analysis. On the other hand, when an overlap occurs while capturing a meaningful image, it is a complex task to eliminate the overlap and stitch the parts of the image back together.
U.S. Pat. No. 4,383,170 issued to Takagi et al. and U.S. Pat. No. 4,516,032 issued to Barr relate to similar image subarea capture methods. Here again it is a complex task to eliminate overlap or gaps between sub-areas and stitch the sub-areas of the image back together.
U.S. Pat. No. 5,771,123 issued to Hamano relates to a variable angle optical wedge in a zoom lens for compensating for hand tremors of a photographer. A variable angle optical wedge provides compensating displacement of the image to obtain a more stable image but does not yield a higher image resolution in terms of PEL density.
An advantage of the present invention is that an inexpensive low resolution camera can be externally fitted with the means of the invention to provide higher resolution image capture of text and exhibit details without complex image stitching or edge matching.
A further advantage of the invention is that object distances and magnifying lenses need not be altered in order to achieve higher resolution.
A still further advantage is that small easily controlled light ray deflections are used in the invention and therefore angular distortion is minimized.
An even further advantage of the invention is that partial images of-an object are avoided and therefore, there is no need for complex edge matching or stitching of partial images
These and other advantages which will become apparent from a study of the specification and drawings are obtained by the instant invention through the use of a unique combination of optical and electronic means. Optical wedge action is used in the invention to create multiple overlapping low resolution images of a whole object. Electronic means are then used to construction a high resolution image of the object by interleaving the picture elements of the low resolution images.